Tuberculosis is a chronic infectious disease caused by the Mycobacterium tuberculosis-complex (MTB-C) bacilli, which currently includes the following species: M. tuberculosis, M. bovis, M. microti and M. africanum. 
According to the World Health Organization (WHO), there are 8,000,000 new cases of tuberculosis and some 3,000,000 people die every year. It is believed that there are 2,000,000,000 people infected worldwide.
The current vaccine used as a preventive treatment against tuberculosis is based on bacteria from the so-called BCG strain (Calmette-Guerin bacillus), a variety of M. bovis. 
On the one hand, according to the WO-A-03018053, this is the best vaccine currently available to induce immunoprotection against tuberculosis. However, the safety and the effectiveness of this vaccine in humans remain controversial in some countries because it does not completely protect adults against pulmonary tuberculosis.
On the other hand, WO-A-03004520 describes as a known fact that the most effective treatment to fight tuberculosis in infected people, both for those who have and those who have not developed the disease, consists in the administration of several drugs, including isoniazid, for a period of several months.
This prolonged treatment may induce the development of microorganisms resistant to these drugs when the treatment is not completed and, moreover, the aforementioned drugs only act when the bacillus has an active metabolism (i.e., when it is growing) but not when it has a non-active metabolism. This is a significant inconvenience because during tuberculosis infection bacilli coexist in both an active and a non-active metabolism phase.
One possibility to solve these problems, as described in the patent U.S. Pat. No. 4,724,144, consists in the use of an immunotherapeutic agent based on dead M. vaccae cells as an adjuvant for the treatment to tuberculosis together with the administration of other drugs, such as rifampicin and isoniazid.
However, patent U.S. Pat. No. 6,001,361 states that such an adjuvant agent has not been used in large-scale vaccination of people against tuberculosis, and there is little information on its effectiveness.
Therefore, an immunotherapeutic agent is needed for the treatment of tuberculosis to act as a coadjuvant for these drugs, and this agent must not induce the development of resistant microorganisms and also generate immunologic response even against bacilli in a non-active phase.
The authors of this invention have discovered a method that allows the preparation of a new immunotherapeutic agent useful for the combined treatment of tuberculosis in association with other drugs. This immunotherapeutic agent contains cell wall fragments of a virulent MTB-C strain that may increase the effectiveness of the associated drugs to generate an effective immunologic response against bacilli that are not in an active metabolism, thus also reducing the risk of resistance.
The object of this invention is to provide a method to obtain an immunotherapeutic agent containing cell wall fragments of a virulent MTB-C strain, useful for the combined treatment of tuberculosis in association with other drugs.
The immunotherapeutic agent obtained using the previous method and the use of this agent for preparing a drug for the combined treatment of tuberculosis in association with other drugs are also included in the object of this invention.
Moreover, another additional object consists in the pharmaceutical compounds made with this immunotherapeutic agent.